1. The Field of the Invention
The subject invention relates in general to a data bus system that uses coaxial type cable for signal conductors, with multiple signal ports/taps. Specifically, the invention relates to an improved data bus system, for interconnecting the maximum number of data ports to the network without using repeaters or other electronic aids.
2. The Prior Art
In many data bus systems in use today, a coaxial type cable (or other wire type cables) is used for bussing a main signal, with multiple signal ports/taps interconnected to the coaxial bus. To date, these interconnections have been achieved by terminating the coaxial cable each time a port/tap is added. The number of taps that can be used on such a system is primarily determined by the electrical effects these taps have on the signal being conducted along the signal path. The tap's electrical effects on the data signal are caused by the tap and its electronics, which load the line. Electrical effects on the data signal are further influenced by the physical configuration of the tap connection, which causes an impedance mismatch in the line.
Therefore, the number of taps that can be connected to presently available data bus systems is a relatively small number. In many applications, this number is not sufficiently large enough to meet the systems needs, and electronic devices, such as repeaters, are used along the bus in order to allow sufficient data ports to be used. Expanded use of such devices in data distribution systems add significantly to the cost, and limits the economic attractiveness of the system.
U.S. Pat. No. 4,120,554, entitled, "Coaxial Cable Connector," teaches a tap for electrically contacting with a coaxial cable, and is hereby incorporated by reference. Pursuant thereto, a connector tap is disclosed for probing the center conductor of a coaxial cable, and functions to permit electrical sampling of the main signal without requiring a termination of the cable. Such a device works well, and has been accepted by the industry. However, even with such devices, the maximum number of data ports to a bus network has heretofore been limited due to the electrical effects these taps have on the signal being conducted along the signal path. Therefore, the industry has been in need of a data bus network which would permit a sufficiently large number of data ports to be used in tapping a coaxial bus, without the use of repeaters or other electronic aids, which add cost and electronic complexities to a system, and thereby affects the systems reliability. Moreover, it would be desirable to provide electronic isolation between the main bus and the peripheral data ports.